Better handling of tokens near expiry

[ponyisi]

Resolves #473:

• if an auth token is within 60 seconds of expiry, renew it before proceeding with request;
• if a transformation status query returns an auth error, attempt a retry with an updated token;
• add better handling of other error codes when querying transformation status.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.29%. Comparing base (7e09033) to head (e776afb).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #487      +/-   ##
==========================================
+ Coverage   82.96%   84.29%   +1.32%     
==========================================
  Files          26       26              
  Lines        1403     1515     +112     
==========================================
+ Hits         1164     1277     +113     
+ Misses        239      238       -1     

Flag	Coverage Δ
unittests	84.29% <100.00%> (+1.32%)	⬆️

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[ketan96-m]

looks good!